A stroke is the result of a disturbance of the blood supply to the brain. This happens because an artery is blocked by a blood clot, called an ‘ischaemic’ stroke, or if a blood vessel bleeds in the brain, called a ‘haemorrhagic’ stroke.

The consequences of an arterial obstruction depend on which part of the brain is denied oxygen by the affected blood vessel and the extent of the blockage. Mild strokes or ‘transient ischaemic attacks’ are caused by limited blockage and with stroke symptoms that last less than 24 hours before disappearing. Symptoms of mild strokes or strokes may include speech, swallowing or visual impairment as well as paralysis of one side of the body or partial paralysis. If a person suffers a stroke, this can cause permanent damage to the brain—the functional disturbances of the brain may resolve over a long period of time or are never fully resolved. It is important to seek immediate medical attention to restore normal blood flow as soon as possible and to prevent the most serious complications of this type occurring which could include death.


  • Sudden paralysis or weakness in the face, arms or legs, in particular on one side of the body
  • Sudden confusion or impairment of speech or understanding
  • Sudden vision impairment in one or both eyes
  • Sudden gait disturbance, dizziness, or balance or coordination impairment

The figure shows the blockage of arterial blood supply by a blood clot.

MAT-GB-2002255 (v2.0) October 2021